The present invention generally relates to tilt steering columns for automotive vehicles and more particularly to an apparatus for releasably locking a tilt steering column in adjusted opposition.
Many automobiles have steering columns which can be tilted to an adjusted position selected by the vehicle operator. A locking mechanism is typically provided to maintain the steering column in its selected position. The known locking mechanisms include pawl-and-rack and rotary actuated designs. The known pawl-and-rack designs tend to be relatively complex and have difficulty in maintaining the steering column in its selected position when considerable force is applied to the steering column in a direction that is highly skewed to the axis of the steering column.
The rotary actuated designs appear to be relatively less complex, but in practice must address issues relating to vibration of the steering column as a result of the lash within these mechanisms. Attempts to minimize lash to thereby attenuate the vibration of the steering wheel typically utilize highly toleranced components and the matching of components to minimize lash and as such, these mechanisms tend to be relatively expensive to manufacture and service.
In one preferred form, the present invention provides an apparatus for releasably locking a tilt steering column of an automotive vehicle. The apparatus includes a housing, a rack, a first coupling member, a rack trunnion, a pawl member, a second coupling member, a pawl spring and a locking member. The housing has a central cavity and a slotted aperture that is formed through the housing and intersects the central cavity. The rack has a first trunnion mount and a rack body. The rack body includes a plurality of rack teeth and a first coupling aperture into which the first coupling member is disposed. The rack trunnion has a wall member and a first pivot trunnion. The wall member has a second coupling aperture formed therethrough, the first coupling member extending into the second coupling aperture and coupling the rack to the rack trunnion such that the rack and the rack trunnion are movable relative to one another along an axis that is generally perpendicular to an axis of the first coupling member, the first pivot trunnion being disposed in the housing and defining a first pivot aperture, the first pivot aperture being aligned to the slotted aperture. The pawl member has a second trunnion mount, which defines a second pivot aperture, a plurality of pawl teeth, which are configured to meshingly engage the rack teeth, and a locking cam. The second coupling member is disposed through the slotted aperture, the first pivot aperture and the second pivot aperture to pivotably couple the pawl member and the rack trunnion and slidably couple the housing to the pawl member and the rack trunnion. The spring is coupled to the pawl member and biases the pawl teeth out of engagement with the rack teeth. The locking member is coupled to the housing and extends into the central cavity. The apparatus is operable in an engaged condition, wherein engagement between the locking member and the locking cam of the pawl member overcomes the spring and rotates the pawl member toward the rack to cause meshing engagement of the pawl teeth and the rack teeth and thereby inhibit relative movement between the rack and the rack trunnion. The apparatus is further operable in a disengaged condition, wherein the spring rotates the pawl member away from the rack such that the pawl teeth are not meshingly engaged to the rack teeth to thereby permit relative movement between the rack and the rack trunnion.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.